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A) INTRODUCTION

It is commonly stated that the natural hydrograph is the key element in restoring wildlife, such as the endangered pallid sturgeon, the endangered least tern as well as the threatened piping plover, on the River (USFWS, 2000). The U. S. Fish and Wildlife Service’s (USFWS) 2000 biological opinion stated that the present management of the Missouri River is causing jeopardy to the three species. The biological opinion proposed modifications of the present hydrograph on the Missouri River in an effort to more closely mimic the natural hydrograph is the cornerstone of the efforts to manage the river to benefit the native species. The proposed modifications, which include a ‘spring rise’ followed by a ‘summer low flow’ and a resulting ‘high fall flow’ does not match the natural hydrograph. The management actions being advocated in the biological opinion for the Missouri River are largely based on an assumption that the natural hydrograph was beneficial to the pallid sturgeon, the piping plover, and the least term. However, it must be emphasized that restoring the stream requires much more than just modifying the flow. The flood hydrograph is only one element of many that affects the Missouri River environment. Specifically, the biological opinion requests flow modification to a spring rise and summer low flow below Gavins Point Dam (fig. 1) There is special interest in the non-channeled reach from Gavins Point to Ponca, Nebraska, because this reach still has sandbars that are presently utilized by the piping plover and least tern for nesting (Jorgensen, 2003a). However, numerous questions should be answered before it can be ascertained that a logical management alterative can be created.

One question is, even if flow were reverted back to the natural hydrograph, would that ensure or even likely ensure ‘restoration’ of the river in the biological sense? The probable answer to this question is that the present condition of the river is the result of many more factors than just flow. Flow may not be the controlling factor at all. There are many other changes that have been made, which pragmatically are irreversible, that will reduce or nullify any perceived improvements that are anticipated from flow modification. Significant changes, such as land use, water quality, tributary conditions, and the introduction of nonnative fish, all of which are not related to the USACE’s management of the river would likely critically limit “restoration or recovery” even if the channel stabilization structures and dams were removed from the main stem Missouri River. Tributary changes are having a large impact on conditions in the river. Contaminants have been introduced via the tributaries; small dams even on the smallest tributary watercourses have altered both the flow and the sediment discharge (Jorgensen and others, 2002; Jorgensen, 2003b). These small impoundments have been stocked with millions of nonnative fish, most of which are predator species, and all are competitive to the native species (Tyus, 2002). In reference to the Missouri River, the construction of major dams and impoundments of large sections of the river and its tributaries, are just some of the changes that cannot be nullified by simply altering flows at Gavins Point Dam. Junk and others (1989, pp. 110 and 122) warn that applying the ‘flood-pulse’ concept cannot be expected to be successful in all situations:

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